Molecular dynamics method is used to simulate the influence of the mesopore size and structure on the heat transport characteristics of the mixed nitrate. The Material Studio software is used to establish the mixed nitrate models of different scales and two structures, and the NaNO₃-KNO₃ models of different proportions that reach the eutectic state. By calculating the models and sorting out the calculation results, the phase transition of mixed nitrates on a nanometer scale is calculated and the micro-mechanism of heat transport characteristics is analyzed. The results show that the phase transition temperature of the solar salt first increases and then decreases with the increase of the nanopore size, and finally is consistent with the melting point on a macro scale. The proportion of cations has a great influence on the phase transition temperature of mixed nitrate, and the nanowire structures also change the phase transition temperature of nitrate. The bulk thermal expansion coefficient of nitrate decreases with the increase of mesoporous size, increases with the increase of NaNO₃ content, and changes with the mesoporous structure. The enhancement of the interaction between ions will increase the thermal conductivity, but it will not have much effect on the specific heat capacity at a constant pressure.